Variable delivery force pump



Patented July 27, 1954 VARIABLE DELIVERY FORCE PUMP Leo Peter Widmer, Rio de Janeiro, Brazil, and

Theodor Mller, Winterthur, Switzerland, as-

signors to Schweizerische Lokomotivund Maschinenfabrik, Winterthur, Switzerland Application November 20, 1951, Serial No. 257,278

Claims priority, application Switzerland November 29, 1950 (Cl. 10S- 37) 19 Claims.

This invention relates to a variable delivery force pumphaving a plurality of plungers driven by a single swash plate of constant inclination in which, by axial displacement of both the plurality of plungers and the swash plate relative the pump drive shaft, the effective throw of the plungers is varied.

An object of the instant invention is to provide control means for automatically and under the pressure of the liquid being pumped to axially displace both the swash plate and the plurality of pumping plungers of variable delivery force pumps.

A further object of the invention is to decrease automatically the delivery of the pump on increased delivery pressure and automatically to increase the delivery of the pump on decreased delivery pressure without any substantial loss in pump eiciency.

Still a further object of the invention is to provide a variable delivery pump control means in which the resultant force of the control means for automatically varying the throw of the delivery plungers is always substantially coaxial with the pump drive shaft for all displacements of the rotatable swash plate axially the drive shaft.

The foregoing, and other obvious, objects of the instant invention are accomplished by providing a control means coaxial with the pump drive shaft, and in modied embodiments a plurality of auxiliary control means symmetrically disposed with respect to the pump drive shaft, responsive to pressure prevailing in a compartment to which the pumping plungers deliver the pumped liquid, the control means displacing a swash plate of constant inclination to the drive shaft from a minimum displacement, corresponding broadly to the maximum delivery of the pumping plungers, to a predetermined maximum displacement, corresponding broadly to the minimum delivery of the pumping plungers, with preferably a sudden and relative instantaneous displacement of the swash plate from a predetermined intermediate displacement to the maximum displacement thereof.

The invention is more completely described in the following specification with reference to the drawings which disclose illustrative embodiments thereof and in which:

Figure l is a vertical section through a first illustrative embodiment of a variable delivery pump with vertically positioned pumping plungers having one control means axially positioned relative to the drive shaft of the pump;

Figure 2 is a vertical partial section through a modified illustrative embodiment incorporating in addition to the axial control means of the embodiment of Figure l one or more auxiliary control means non-axially disposed with respect to the drive shaft; and

Figures 3 and 4 are vertical partial sections of illustrative modified auxiliary non-axial control means.

While the pump housing I, together with its main bore 2, and its plunger bores, 3 and 3', is shown in the drawings with the principal pump axis in vertical position, the pump may be in other spatial positions, for example horizontal. The plurality of plunger bores, 3 and 3', for example twelve, are disposed circularly about the axis t in the lower end of housing I in the region of the reduced portion 2 of the main bore andl each has its axis parallel to the pump axis 5. In the illustrative embodiment bores 3 are for delivery plungers l of a relatively large diameter and bores 3 for plungers fi of smaller diameter, and may be arranged alternately a larger and a smaller bore or in groups of the same size circumferentially and with each bore axisl substantially equidistant from its adjacent bore axes. The number lof larger diameter plungers may differ from the number of the smaller diameter plungers, that is for the stated number of twelve, need not be six each. Thus there may be ema ployed eight or nine larger diameter plungers,

the others being smaller diameter plungers of which each is positioned in the pump housing about the main bore between successive groups of the larger diameter plungers.

of diameter and cross section in the embodiment of Figure 1 may, however, be of the same diameter and cross section. The pump housing is disposed either as shown in Figure 1 in a reservoir of the liquid to be pumped so that the liquid inlet bores are at all times below the surface of the reservoir liquid, with the upper pump portion extending out of the reservoir, or in a reservoir comy on the' pump drive shaft I3 positioned with its` axis coincident substantially with the principal The bores and plungers, while shown as of two diiferent sizes axis 6, and rotates with the shaft but is axially displaceable on the shaft. The lower end of each spring is seated in a recess 6l in a ilange ring I integral with a bushing I6 which is slidably tted into the smaller portion 2 of the main housing bore so that the flange ring I5 rests, when the pump is at rest as shown in Figure l, on the annular shoulder I'I of the main bore formed by the reduction of the main bore 2 to its smaller portion'2'. The drive shaft i8 is driven by a motor I9 positioned on the pump cover 25, the motor having a stub shaft extending into the upper end of shaft I8 and connected thereto by a key 22. The upper end of drive shaft I8 is journalled in the cover 25 by means of the bearing 20, while its lower end, which extends into bushing I6, is journalled in bushing IE5 by means of a bearing 2i. Through the roller bearing 23 the swash plate I3 is supported against the guide member 24 which is axially displaceable in the upper portion of the main bore 2 and is pressed downwardly by the pump main spring 2'I braced between the guide member and the pump cover.

Each plunger bore, 3 and 3', is provided with a radial intake bore, 29 and 28, from the plunger bore to the exterior of the pump housing I and below the surface of the liquid 26 in the reservoir 5. The position of the radial bores 28 and 2S longitudinally of the principal pump axis 6, determines during what portions of the travel of the pumping plungers liquid to be pumped may ilow from the reservoir into bores 3 and 3. Bores 3 are additionally each provided with a suction valve I positioned axially at substantially the lowermost throw position of the plunger d', in order that even when the radial bore 28, positioned upwardly from valve l, is sill closed by the plunger Il', the latter will nevertheless draw liquid from reservoir into the bore 3'. Suction valves 'I of the bores 3 may however be omitted, in which event the radial bore 28 will also control the drawing of liquid into bore 3 in the same manner as radial bores 29 for plunger bores 3. Liquid 26 is drawn into the bores 3 and 3 from the reservoir during the suction strokes of plungers 4 and 4 and then, on the delivery strokes of the plungers, or more accurately that portion thereof during which the plungers close the respective radial intake bores, is forced through the respective spring pressed ball valves 3D and 3|, positioned at the lower ends of the plunger bores, into the pump pressure chamber 32, from which it is conducted to the point of use by the delivery pipe 33.

It will be noted from Figure 1, which shows the pump at rest, that the axial distance between the bottom of cover and the top of guide member '24, which is pressed by main spring 2l against a shoulder 24 limiting its downward movement, is such that with the guide member moved axially upward its maximum against the pressure of the main spring, the most upwardly positioned of the radial intake ports, 2,8 in Figure 1, will be opened by its plunger. Preferably also such distance is such that with the guide so displaced to its uppermost position, and hence also the swash plate I3 under the influence of the delivery plungers and their spring 8, the heads of the plungers will still be in contact with the ring 9, thereby eliminating shock impacts and excessive wear attendant thereupon. Ring 9 may swash plate, need only be replaced in the event of undue wear,

Below the lower bearing 2| in which the lower end of the drive shaft I8 is journalled in bushing I6, a disc Ul is affixed to the bushing l5 and serves as the upper seat of a spring 35, which spring is of such configuration and magnitude that it exerts a greater force upwardly on disc III and hence bushing I6 and its integral flange ring I5 than the force of all the springs 8 exert downwardly on the ring I5 in the rest position of the pump. The lower hub end of the swash plate i3 is supported axially on the ring I5 and bushing I6 by a roller bearing 3l, so that the swash plate I 3, the bearing 3'I, the ring I5 and the bushing I 6 are tensioned constantly, and thus move as a unit upwardly and downwardly axially on the drive shaft I8.

The lower end of the spring 35 bears against a plate fi@ extending across and iixed in the reduced portion 2 of the main bore and at some distance axially below the disc M. Plate 40 has integral therewith on its lower face a cylinder @ila and integral with its upper face a second cylinder 49h having a substantially smaller internal diameter than has the cylinder 48d.. Each nevertheless be omitted and the plunger heads made to bear directly on the swash plate, but the ring 9 is preferred so that it, rather than the f' and the lower rim face of the bushing i5.

of the cylinders 'a and llt?) is coaxial with the driving shaft i8, while the plate i0 forms the upper or cover wall of the pump pressure chamber 32. A mushroom type valve 34 bears with its upper end against the disc I4 and extends downwardly through the coaxial cylinders a and dill). The stem of valve 34 is of such length that only the lower face of its enlarged head 39 is permitted to extend, by means of a stop or other known means, in the position of minimum axial displacement of the swash plate and with the upper end of valve 34 bearing against the disc I4, out of the lower end of cylinder 46a but with such lower face away from the bottom of the pressure chamber 32. ln the vertically positioned embodiment of the invention and as shown in Figure l, the stern of valve 3d. is preferably of smaller diameter at its head end than at its upper end, and the cylinder dile is provided with a radial port il in the region of the cylinder toward the plate dit, that is in its upper end region, and the cylinder Mib with a radial port I2 at a predetermined distance axially upward from the plate. Port di is thus normally open, and connects the air containing compartment di, formed by the lower face Ml of the plate du, the upper face 45 of valve head lig and the walls of cylinder Illia, by the pressure chamber 32, whereas port normally closed by the unrecessed upper portion of the stem of valve 343, connects to the pressureless chamber 38 formed between the upper face of platev GG, the walls of the reduced portion 2 ci the main pump bore, the lower face of disc Id The recessed portion of stem of valve 34 is of such length axially that when the upper end of the valve head 39 closes the radial port il the upper end of the recessed valve stein opens port d2. It

"is thus apparent that when the surface of valve head 39 comes to rest upon the lower face ad of the plate s0, the maximum displacement of the swash plate i3 and all of the axially displaceable elements is xed. The surfaces it and d5 are iinished accurately to fit each other so that no. or substantially no, liquid leakage occurs when they are seated on each other.

The mode of operation is as follows: On rotation of the drive shaft i8, the swash plate I3 rotates therewith and the plungers l and 4 are in the position shown in Figure l, in respectively their lowermost position of the start of the delivery stroke and the lowermost position of the start of the suction stroke, with radial bore 29 substantially completely unlocked by plunger 4 and liquid illing the bore 3 from the bore 29 to the closed ball valve 3|, and the radial bore 28 closed, suction valve l closed and perhaps no liquid, or only a residue from the previous delivery stroke, in the bore 3' between the plunger d and the closed ball valve Sli. As plunger 4 is depressed by the swash plate against the plungers spring il, bore 29 is first sealed by the plunger in its downward path, the pressure of the plunger on liquid in bore 3 is transmitted to ball valve 3| which opens, the plunger for the remainder of its downward throw, to the position shown in the dashed line across bore 3 in Figure l, ejecting the confined liquid into the pressure chamber 32. While the plunger is moving downwardly, plunger 4 under the action of its spring t moves upwardly for the suction stroke during all of which the suction valve 'l is open, ball valve remaining closed, until the plunger 4 reaches the upper limit of its throw, shown by the dashed line across bore 3', during no part of which throw it will be noted is the bore 28 opened by the plunger with the swash plate I3 axially in its lowermost position shown in Figure l. On continued rotation of the swash plate, plunger 4 e moves through its entire suction stroke upwardly with ball valve 3| closed by its spring and the suction, with liquid iiowing into 'the bore 3 only after the plunger has passed bore 29; and in the meantime, plunger 4 travels downwardly on its delivery stroke, valve 1 closing on commencement of the delivery stroke and ball valve 39 opening at such time and remaining open for the whole of the delivery stroke so that plunger 4 ejects the liquid coniined in bore 3 into the pressure chamber. Assume now that liquid, as the result of not being drawn ori quickly enough by pipe 33 to the point of use, commences to accumulate in the pressure chamber. As the level of the liquid under pressure in the pressure chamber rises, valve head 39 is forced upwardly in cylinder 43a. As before stated, this will force the entire axially displaceahle assembly of elements, including valve 34, disc it, bushing I5, ring I5, swash plate i3 and guide member 24, together with the intervening plunger springs 8 and the various bearings, upwardly against main pump spring 2l. The plungers 4 and 4 are thus also moved upwardly in their bores with the obvious result that at least the effective delivery stroke of plungers 4 is decreased, since when displaced upwardly the plungers :i in the initial position of their delivery stroke will leave their bores 2Q open for :re-expulsion therethrough of the liquid drawn in on the suction stroke. As is obvious from the drawing, the residual portion of the delivery stroke during which confined liquid in bores 3 is ejected into the pressure chamber 32, is the less the higher the swash plate is displaced axially. In fact, the residual portion of the delivery stroke may be made substantially zero providing the maximum upward displacement of the swash plate is properly predetermined, so that no liquid is eii'ectively pumped or delivered to the pressure chamber by the plungers 4. With the swash plate displaced axially upward to an extent that at no time the plungers A open their respective ports 28, the liquid delivered by plungers il to the pressure chamber remains substantially unchanged from that delivered with the swash plate in its lowest, or minimum, axial position. However, when the swash plate is displaced axially that the plungers 4 in their strokes do uncover the respective bores 28, the liquid delivered thereby is decreased in similar fashion substantially as for the plungers 4.

The displacement of the valve head 39 upwardly is not the only force which tends to move the axially displaceable elements upwardly. As the back pressure on the plungers 4 and 4 delivering liquid increases, the total sum of such pressures also tends to compress the main spring 2l, by way of the springs 8, and thus aids in varying the total delivery. Thus if the pressure which the plungers have to overcome is large, main spring 2l is increasingly compressed and, as a result of the smaller eective throw of the plungers 4, and, at a predetermined point, also of the plungers 4 in bores 3 provided with the suction valves 7, less liquid is delivered to the pressure chamber, and viceversa. Thus without loss in elciency, the liquid pumped and delivered is automatically decreased on increased delivery pressure and increased on decreased delivery pressure.

The pressure within the pressure chamber thus may rise to a predetermined maximum amount, and since the ports 4| and 42 are at such predetermined locations relative to each other that the upward movement of the valve head closes port 4i while simultaneously the recessed portion of the stem of valve 34 opens port 42, such maximum hydraulic pressure forces the valve head 353 quickly upward until the upper surface 45 of the valve head rests rmly against the lower surface 44 of plate 4Q. Thus the swash plate is axially displaced against the pressure of the main spring 2l to its uppermost and maximum position, and on continuous rotation while still actuating the plungers 4 and 4 has reduced the effective delivery throw of both to substantially zero. It will be noted that by positioning the ports 4| and 42 at predetermined greater or lesser distances from the surfaces of the iixed plate dll, and where required increasing or decreasing the length of the recessed portion of the stem or" valve 34, the position at which the sudden upward movement of the entire axially displaceable assembly occurs, may be predetermined. For the eventuality that pumped liquid may leak into the compartment 4l from the pressure chamber 32 while port 4| is open, which leakage fluid on closure of port 4| will be ejected around the recessed portion of the stem of valve 34 on further upward movement of the valve head 39 through the port 42 into the relatively pressureless chamber 38, a small outlet opening It is provided .in the disc i4, by way of which liquid accumulated in sudicient quantity in the pressureless chamber 38 may be drawn oir and returned to the :reservoir. It will be noted, however, that notwithstanding accumulation of any such leakage liquid in the pressureless chamber, the pump will continue to operate. Thus, even if the accumulated liquid in the pressureless chamber 3! should be above the level of disc lll in its lowermost position, namely the position of Figure l, the displaceable combination will not be markedly impeded in its downward movement toward such lowermost position by such accumulated leakage liquid which will in part pass through the opening lli and in part, while bore :l2 is open, drain back to the compartment 4l and drain therefrom through port 4| back into the pressure chamber 32 when the port 4| is being opened by valve head 3d until such time as the upper face 45 of the valve head is below the lower edge of open port M. If desired, the port dl and l2 may be eliminated, in which event there is no sudden upward movement of the displaceable combination, only a continuous gradual upward movement until surface 45 of the valve head 39 cornes to rest against the surface 44 of the plate lill.

The embodiment of the invention shown in Figure 2 includes all the elements of the embodiment of Figure l except the bearing 3l positioned between the lower hub of the swash plate and the iiange ring I5 integral with bushing I5. As a substitute for such bearing and to transmit the axial movement of the ring I5 directly to the guide member 24, flange ring I5 has aixed thereto and preferably integral therewith, a hollow cylindrical collar 50 iitting into the main bore 2 and of a height such that its upper rim abuts the lower rim of guide member 26. In this embodiment then, the pressure of the control valve 34 is transmitted from the disc U5, bushing I5, integral flange ring I5, and hollow collar 56 directly to the guide member, saving wear on the axial bearing 23 between the upper face of the swash plate and the guide member. In addition the embodiment of Figure 2 has two or more laterally positioned auxiliary control valves 34 (one is shown in the gure) to produce a sudden conversion of the axial displacement from one which increases uniformly with increasing pressure to one which, as the predetermined pressure of the liquid within the pressure chamber 32 corresponds to the predetermined displacement below maximum displacement, substantially instantly passes from the predetermined displacement to the maximum displacement. The auxiliary control valves 34 are disposed symmetrically about the principal pump axis 6 in individual bores in the pump housing so that the resultant of the forces they apply to the flange ring I5 lies on the principal axis 5 together with that of the axially central control valve 34. Auxiliary control valves 34 and the bores in which they operate are respectively of construction and form similar to the control valve 34 and the cylinders llila and lllb, with their enlarged heads 39 on and in contact with bores Alia and the stems of valve Bil in bores Mb', the non-head ends of the valves 3d bearing against the annular flange I5. The radial port 132 of each bore 40h is above the surface of the liquid in reservoir 5, that is, opens to the external atmosphere. The radial port All opening into the portion of bore 40a' between valve head 39 and bore 45h', is connected by way of a channel 59 to the pressure compartment 32, the channel also being connected to a radial bore 59 which opens into the portion of the bores alla below the valve head 39'. Liquid under pressure is thus suppliable by channel 59 and radial bore 59 to below the valve head 39 and when supplied forces the head upwardly even though some liquid under pressure may flow through the radial bore 4I into the portion of bore lla above the head 39' since the upper surface of the head is less (by the area of the stem) than the lower surface of the head acted on by the liquid pressure. With increasing liquid pressure the valve head is slowly moved upwardly by the resultant force and the bore 4I is closed by head 39', and on such closure, the portion of lesser diameter of the valve stem 34 opens the bore d2', permitting the liquid above the head to be expelled therethrough on further upward movement of the head. This unimpeded expulsion of the liquid above the head causes the valve 34 to accelerate the speed of its motion in the direction of the maximum displacement of the annular flange I5. With descreasing liquid pressure in pressure chamber 32, and the consequent displacement of the valves toward the position of minimum displacement, the liquid below the valve head drains back into the pressure chamber.

1n Figure 3 a modified form of auxiliary control valve means is shown. The auxiliary control valve of this embodiment is essentially a plunger 5I of uniform diameter its length provided in bores in the pump housing disposed symmetrically about the principal axis 6 as in the case of valves 345', with the upper ends 52 of plungers 5I acting directly on the annular flange I5 under the pressure of liquid from channel 5d connected to the pressure chamber 32 from the lower end of the bores housing the plungers 5I. It is obvious that the plunger 5i is at all times under the same pressure as prevails in the pressure chamber. In a further modification of the auxiliary control valve means of the type employingr plunger 5I, the region of its housing bore below the plunger 5i may be connected to an adjacent liquid delivery plunger bore 3 rather than to the pressure chamber. This modication is also shown in Figure 3, where the channel 5l, shown in dashed lines, connects such region of the plunger bore to the bore 3 of the delivery plunger 5' in the region of bore 3 below plunger Il', and a spring 58 presses from the bottom of the auxiliary plunger bore against plunger 5I forcing it at all times against annular flange I5, the channel 55 being eliminated in this modification. By means of channel 53 the auxiliary plunger 5I in this modiiication exerts an upward pressure against the annular iiange I5 due to the eiiect of liquid pressure only during the delivery stroke of plunger 4', and spring 68 prevents plunger 5I from leaving the annular flange during the suction stroke of plunger 4. In such modification, it will be noted that the bore 3' has itself been modified by the elimination of the suction valve 'I of Figure l. A particularly advantageous application of the last described auxiliary plunger-type control means is given when the pump, as shown in the illustrative embodiment of Figure l, has delivery plungers of two diameters respectively, each of the smalier diameter delivery plunger bores having a cooperating auxiliary control Valve of this type, and the sum o1" the cross-sectional surfaces of the auxiliary control valves and the small diameter liquid delivery plungers is equal to the crosssectional surface of the larger diameter liquid delivery plungers. In such case the pressure exerted by the auxiliary control valves and the delivery plungers of the two diameters on the main spring 2i is equal to that similarly exerted in a pump of which all the delivery plungers are of the larger of the two diameters.

The sudden quick displacement of the axially displaceable elements from the predetermined displacement to the maximum displacement may also be obtained by providing auxiliary control valves of the type of which one is shown in Figure 4. Auxiliary control valves 55 are disposed in the pump housing in the same manner and locations as are the auxiliary valves Sil of the embodiment of Figure 2 and valves 5I of the embodiment of Figure 3. Valve 55 is essentially a plunger having lower integral skirts of the same diameter as the plunger, within the hollow skirt of which a spring 51 presses the plunger continuously against the annular flange l5, the total length of the valve and its integral skirt beingsuch that in the position of minimum displacement shown in Figure 4, bore 59, or a plurality thereof through the outer cylindrical surface of Athe skirt, is at the bottom substantially of an ,enlarged portion of the bore 58, in the low-- er and upper unenlarged portions of which the valve 55 is a sliding t. An exhaust bore 60 connects the enlarged portion of bore 5B to the external atmosphere, while somewhat below this enlarged portion the liquid channel `55 connects the bore '5S to the pressure chamber 32. In the position of minimum displacement, channel 56 is closed vby the plunger skirt and, as shown in Figure '4, remains closed thereby until, on reaching a predetermined displacement, the skirt opens channel 55. Prior to the opening of channel 56, the plunger bore region below valve was under no pressure, being connected to the external atmosphere through 58, 59 and 60. The position of the bore 59 through the wall of the plunger skirt from the free end of the skirt is such that withchannel 56 opened, fthe lower edge 62 of the bore .59 will be above the upper edge 53.of the enlarged portion of bore 58. Hence the external connection through the bore 60 is now closed, and valve .55 now subjected to the same pressure as prevails in the pressure chamber. As the result of this suddenly applied additional force by the auxiliary control valves 55, for example two .at diametrically opposite portions vof annular flange l5, the hollow cylinder 50 forces the guide l2li almost instantly into its positionof maximum displacement.

It .willbereadily apparent that various modications in, and embodiments of, the variable delivery Dump `of lthe instant invention as disclosed by way of illustrative embodiments may be made without departing from the spirit of this invention. Some have `previouslybeen discussed and illustrated, others vmay include -using the auxiliary control valves of any of Figures 2, 3 and 4 in selected .groupings in a given pump some of .onetype and some of the other or both other types, or having the valve springs 8 beardirectly against the main bore shoulder ll by eliminating the spring recesses 61 .in the annular ange l5 and substituting therefor larger openings in the ilange which permit the plunger valve Springs to pass through the flange without interference, or eliminating the axial bearing 3l even in pumps-having no hollow collar 50 and substitutingtherefor a spacer shell 66 (see -Figure 1) to transmit the'pressure of controlvvalve 34 from bearing 20 to swash pla-te I3, etc.

`What we claim is:

l. A variable delivery force pump comprising a housing, a main bore substantially central and axial of the housing, a rotatable drive `shaft substantiallycentral of the main bore,a fixed plate transverse of the main bore and dividing the mainbore into a iirst and a second compartment, the drive shaft extending through the first compartment toward but not sufficiently to engage the transverse plate, means including a swash plate rotatable with the-shaft axially displaceableon the shaft, the swash plateihaving a predetermined inclination tothe shaft, l,a plurality of secondary bores parallel `to the drive shaft in the khousing below the swash plate, .a plunger reciprocable'ineach vseconda-ry bore, an inlet :bore extending to a point external ofthe housing for each secondary bore and adapted to be opened and closed by the respective plunger, spring means pressing each plunger against the swash plate, a main spring means pressing the means including the swash plate toward the transverse plate and against the plunger spring means, a liquid delivery bore connecting each secondary bore to the second compartment, and control means extending from the second compartment into the first compartment and bearing against the means including the swash plate to displace the latter means axially of `the shaft against the main spring means in accordance with the pressure prevailing within the second compartment to vary the effective pressure stroke of the plungers.

2. A variable delivery force pump according to claim l in which the maximum possible displacement of the control means is not in excess oi' the axial projection of the inclination of the swash plate on thedrive shaft.

3. A variable delivery force pump according to claim 1 in which an auxiliary spring is positioned between the transverse plate and the axially displaceable means including the rotatable swash plate to press the latter in the axial di rection opposite that in which it is pressed by the main spring means.

4. A variable delivery pump according to claim 1 in which the control means is adapted on increasing pressure within the second compartment initially to displace the means including the rotatable swash plate at a uniform rate up to a predetermined pressure and to displace the means including the rotatable swash plate substantially instantly to its maximum possible displacement when the pressure within the second compartment attains the predetermined pressure.

5. A variable delivery pump according to claim 1 in which at least one auxiliary control means disposed in the housing adjacent asecondary bore is connected to the second compartment and is adapted to displace the means including the rotatable swash plate at a rim pOltion thereof `in the same direction as the control means.

6. A variable delivery pump accordingto claim 1 in which the axially displaceable means including the rotatable swash plate comprises a guide member against which the main spring means presses, the guide member being in sliding contact with the main bore, a rst thrust roller bearing between the adjacent end Vfaces of the swash plate and the guide member, a bushing about the end of the drive shaft near thetransverse plate and in sliding contact with the main bore, a second thrust bearing between the ad jacent end faces of the bushing and the swash plate, a bearing within the bushing journalling the end of the shaft near the transverse plate and displaceable axially on the shaft, an annular ange integral with the end of thevbushing adjacent the swash plate, and a port through the annular flange for each secondary bore and registering with the respective secondary bore, the respective plunger extending through the port and the plunger spring means being positioned about the plunger and bearing against the annular iiange and the swash plate end of the plunger' to force the plunger into contact with the swash plate.

7. A variable delivery pump according to claim 1 in which themain bore portion of the iirst compartment has a rst and a second shoulder spaced from each other, and in which the axially displaceable meansincluding the swash plate comprises aguide member in sliding-contact with the 1l main 'bore and of a diameter that its axial displacement is limited in one direction by the first shoulder, the swash plate having its end face adjacent the guide member in a plane substantially perpendicular the drive shaft and its other end face at the predetermined inclination to the drive shaft, the main spring means tending to seat the guide member on the first shoulder, a hub integral with the inclined swash plate face and having its cylindrical wall perpendicular to the inclined face, a rst thrust bearing between the adjacent end faces of the guide member and the swash plate, a ring rotatable on the swash plate hub integral with the inclined face, a second thrust bearing between the inclined face of the swash plate and the adjacent end face of the rotatable ring, a bushing about the end of the drive shaft near the transverse plate and in sliding contact with the main bore below the second shoulder, third thrust bearing between the adjacent end faces of the bushing and the hub integral with the inclined face of the swash plate, a bearing within the bushing journalling the end of the shaft near the transverse plate and axially displaceable with the bushing on the shaft, an annular flange integral with the end of the bushing adjacent the swash plate and positioned above the sec-ond shoulder, and an opening extending through the flange for each secondary core and registering with the respective bore, therespective plunger extending through the opening with the plunger spring means being positioned about the plunger and bearing against the flange and the plunger end nearest to the rotatable ring to force the plunger into contact with the rotatable ring, the :if

main spring and the plunger spring means tending to press the flange against the second shoulder, the second shoulder limiting the displacement of the flange in the one direction.

8. A variable delivery pump according to claim l in which the axially displaceable means including the rotatable swash plate comprises a guide member in sliding contact with the main bore and against which the main spring means presses, the

in sliding contact with the main bore, the end of the shaft near the transverse plate being slidably journalled in the bushing, an annular flange integral with the end face of the bushing adjacent the swash plate, a hollow cylinder of an internal diameter greater than the external diameter of the swash plate integral with the outer rim of the annular flange and of a height to engage the end face of the guide member adjacent the swash plate, an opening in the annular iiange for each secondary bore registering with the respective secondary bore, and the plunger spring means is positioned to bear with its ends against the inten gral flange and the plunger end nearest the swash plate, and in which a plurality of auxiliary control means actuabie by the hydraulic pressure in the second compartment is positioned circularly in the housing adjacent the secondary bores and each auxiliary control means includes a plunger adapted to press the rim portion of the annular flange to displace the hollow cylinder and the guide member in the same direction as the control means.

9. A. variable delivery pump according to claim l in which the control means comprises a valve having a stem and an enlarged head at one end of the stem, an opening substantially central of and extending through the transverse plate, the stem of the valve extending through the transverse plate opening and bearing with its nonhead end against the axially displaceable means, and a hollow cylinder integral with the face of the transverse plate in the second compartment, the hollow cylinder being of such length that the valve head in the position of minimum displacement of the .axially displaceable means is still partially within the hollow cylinder, the valve head being in sliding contact with the internal surface of the hollow cylinder.

l0. A variable delivery pump according to claim l in which the control means comprises a valve having .a stem and an enlarged head at one end of the stem, an opening substantially central of and extending through the transverse plate, the stem having a lesser diameter for a length region` thereof extending from the head than has the stem in the region at the nonhead end thereof, a first hollow cylinder integral with the face of the transverse plate in the first compartment and having an internal diameter such that the non-head region'of the stem is slidably guided on the internal surface of the first hollow cylinder, the non-head end of the stem extending beyond the end of the first hollow cylinder and bearing against the axially displaceable means, a second hollow cylinder having an internal diameter of such dimension that the enlarged head is slidably guided on the internal surface of the second hollow cylinder, the second hollow cylinder being integral with the face of the transverse plate in the second compartment and of such a length that the enlarged valve head in the positionof minimum displacement of the axially displaceable means is still partially within the second hollow cylinder, a first radial bore in the first hollow cylinder connecting the interior of the rst hollow cylinder to the rst compartment, the rst radial bore being closed by the stem portion having the larger diameter for all axial disj placements of the axially displaceable means less than a predetermined displacement, and a second radial bore in the second hollow cylinder connecting the interior of the second hollow cylinder between the plate and the valve head to the second compartment and spaced axially from the first radial bore at such distance that at the predetermined displacement of the axially displaceable means the second radial bore is closed by the enlarged valve head while simultaneously the first radial bore is opened by the valve stem portion of the lesser diameter whereby the valve head under the hydraulic pressure prevailing in the second compartment quickly moves and its integral stem thus simultaneously moves the axially displaceable means from the predetermined displacement position to the maximum displacement position.

1l. A variable delivery pump comprising a housing, a main bore substantially central and axial of the housing, a transverse fixed member dividing the main bore into a first and a second compartment, a rotatable drive shaft positioned substantially centrally in the main bore in the first compartment, means axially displaceable along the shaft on the shaft and including a swash plate of constant inclination to the shaft and rotatable therewith, a plurality of secondary bores in the housing below the swash plate and equally distant from the drive shaft and each other, a plunger reciprocable in each secondary bore, a liquid inlet bore in each secondary bore extending to a point external of the housing and adapted to be opened and 'closed by the reciprocation of the respective plunger on rotation of the swash plate, spring means pressing each plunger against the swash plate, a main spring means pressing the axially displaceable means toward the transverse fixed member, secondary spring means resiliently supporting the axially displaceable means on the transverse fixed member, a liquid delivery Valve bore connecting each secondary bore to the second compartment, and means for displacing the axially displaceable means in accordance with the pressure of the liquid delivered to the second compartment including a plunger extending from the second compartment into the first compartment and bearing therein against the .axially displaceable means, said plunger being aligned axially with the shaft and exerting its force in the same direction against the main spring means as the spring means pressing the secondary bore plungers and the secondary spring means, the axes of the drive shaft, of the secondary bore plungers and of the said plunger being substantially parallel.

12. A variable delivery pump according to claim l1 in which a plurality of auxiliary means for displacing the axially displaceable means is provided Within the region of the housing radially beyond the secondary bores, each of the auxiliary means comprising a liquid bore connected to the second compartment, a plunger Within the liquid bore and displaceable therein in accordance with the liquid pressure Within the second compartment in the same direction as the plunger of the displacing means aligned axially with the shaft and bearing with one end against axially displaceable means, and a venting bore from the liquid bore to a point external of the pump housing, the individual auxiliary means of the plurality being so spaced from each other that the resultant of the forces exerted 'thereby is substantially axially of the drive shaft.

13. A variable delivery pump according to claim 11 in which a plurality of auxiliary means for displacing the axially displaceable means is provided Within the region of the housing radially beyond the secondary bores, each of the auxiliary means comprising a liquid bore, achannel connecting the bottom region of the liquid bore to the second compartment, and a plunger Within the liquid bore of which one end is adapted to engage the axially displaceable means, the said liquid bore plunger being at all times under the pressure of the liquid in the second compartment-the individual auxiliary means of the plurality being so spaced from eachother and relative the driving shaft that the resultant ofthe forces exerted by the said liquid bore plungers on the axially displaceable means is substantially axially of the shaft.

le. A variable delivery pump according to claim 11 in which the means for displacing the axially displaceable means in accordance with the hydraulic pressure prevailing in the second compartment of the liquid delivered thereto is adapted on increasing pressure rtherein to displace the axially displaceable means including the swash plate at a uniform rate up to a predetermined pressure and to displace such means substantially instantly to the maximum possible displacement position when the hydraulic pressure Within the second compartmentattains the predetermined pressure, and'in which a plurality of auxiliary means for displacing the axially displaceable means including the rotatable swash plate is provided within the housing radially beyond the secondary bores, each of the auxiliary means comprisingI a plunger bore of which an intermediate region of predetermined length has a larger internal diameter than the two end portions of the bore, a plunger within the plunger bore, a spring within the plunger bore acting against the plunger to press one vend thereof against the axially displacea'ble means, a chan-- nel from the second compartment to convey liquid thereiromtothe region of the plung-er bore substantially immediately adjacent the intermediate region thereof of Alarger internal diameter, the plunger closing the channel for all displacements o1 the axially displaceable means from minimum to that corresponding to the predetermined pressure, a venting bore from the enlarged intermediate region of the plunger bore to a point external of the pump housing, the plunger closing the venting bore substantially simultaneously With opening the channel, whereby at the predetermined pressure liquid from the second compartment flows into the plunger bore and propels the plunger substantially instantly to the maximum displacement position of the axially displaceable means, and a plurality of openings through the plunger positioned lengthwise the plunger so that at all displacements of the axially displaceable means corresponding Ato pressures less than the predetermined pressure the plunger bore is connected to the venting bore but is disoonnected from the venting .bore at all displacements of the axially displaceable means from that corresponding to the predetermined pressure to and including themaximum displacement.

15. A variable delivery pump according to claim 1l in which a plurality of auxiliary means for displacing the axially displaceable means is provided Within the region of the housing laterally beyond the secondary bores, veach of the auxiliary means comprising .a plunger bore, a displaceable plunger within the plunger bore, a

spring between one end of .the plunger bore and one end of the plunger pressing. kthe other end of the plunger against the axially displaceable means, and a liquid channel connecting the one end of the plunger boreto the region of an adjacent secondary bore below the liquid inlet bore thereof, the individual auxiliary means of the plurality being so spaced from each other and the drive shaft that the resultant of the forces exerted by the respective plunger-s thereof on the axiallydisplaceable means is substantially axially of the drive shaft.

16. A variable delivery pump according to claim Y11 in which the plurality of secondary bores comprises a iirst plurality of secondary bores of a rst diameter and `a second plurality of secondary bores of a second diameter smaller than the first diameter, the reciprocable plungers in the respective secondary bores being of corresponding external diameters, and in which a plurality of auxiliary means for displacingthe axially displaceable means is provided within the region of the housing laterally beyond the secu ondary bores, each of the auxiliary means comprising a plunger bore, a displaceable plunger within the bore, a spring between one end of the plunger bore and one end of the plunger pressing the other end of the displaceable plunger against the axially displaceable means, and `a liquid channel connecting the one vend oi the plunger bore to the region of an adjacent secondarybore of the second plurality of secondary bores below the liquid inlet bore thereof, the individual auxiliary means of the plurality being sc spaced from each other and the drive shaft that the resultant of the forces exerted by the respective plungers thereof on the axially displaceable means lies substantially axially of the drive shaft.

1'?. A variable delivery pump according to claim 11 in which the plurality of secondary bores comprises a nrst plurality of secondary bores of a given diameter and a second plurality of secondary bores of a diameter less than the given diameter, the reciprocable plungers in the respective secondary bores of each plurality being of corresponding cross-sections, and in which a plurality corresponding in number to the number of secondary bores in the second plurality of auxiliary means for displacing the axially displaceable means is provided within the region ci the housing laterally beyond the secondary bores, each of the auxiliary means being positioned adjacent a secondary bore of the second plurality of secondary bores and comprising a plunger bore, a displaceable plunger within and guided by the plunger bore and of a cross-sem tion such that the sum of its cross-section and the cross-section of the reciprocable plunger of the secondary bore o the second plurality oi bores is equal to the cross-section of a reciprocable plunger in a secondary bore oi the iirst plurality of secondary bores, a spring between one end of the plunger bore and one end of the displaceable plunger to press its other end against the axially displaceable means, and a liquid channel connecting the one end of the plunger bore to the region of the adjacent secondary bore of the second plurality of secondary bores below the liquid inlet thereof.

18. A variable delivery pump according to claim ll in which the means for displacing the axially displaceable means in accordance with the hydraulic pressure of the delivered liquid in the second compartment is adapted on inoreasn ing pressure therewithin to displace the axially displaceable means including the rotatable swash plate at a uniform rate up to a predetermined pressure and at the predetermined pressure substantially instantly to the m ximum possible displacement, and in which a rst and a second plurality of auxiliary means for displacing the axially displaceable means are provided within the region of the housing laterally beyond the secondary bores, each of the rst plurality of auxiliary means comprising a plunger bore, a liquid channel connecting the bottom region of the plunger bore to the second compartment, and a plunger Within the plunger bore of which one end is adapted to engage the axially displaceable means under the pressure of liquid in the bore from the channel, and each of the secondary plurality of auxiliary means comprising a plunger bore of which an intermediate region of predetermined length has a larger internal diameter than the two end portions of the bore, a plunger within plunger bore, a spring within the plunger bore acting against the plunger to press an end thereof against the axially displaceable means, a channel from the second compartment to convey liquid therefrom to the region of the plunger bore adjacent the intermediate region thereof remote from the axially displaceable means, a venting bore from the intermediate region of the plunger bore to externally the pump housing, the plunger maintaining the channel closed and the venting bore lid open for all displacements of the axially displaceable means from minimum displacement to that corresponding to the predetermined pressure and on opening the channel simultaneously closing the venting bore whereby at the predetermined pressure the liquid under pressure ilowing into the plunger bore propels the plunger substantially instantly to the maximum displacement position of the axially displaceable means, and at least one port through the plunger in such location thereon to its spring-pressed end that at all displacements corresponding to pressures less than the predetermined pressure the plunger bore is connected to the venting bore and at all displacements exceeding the displacement corresponding to the predetermined pressure is disn connected from the venting bore, the individual auxiliary means of the first and second plurality being alternatively positioned within the pump housing with one auxiliary means of the one plu rality between two auxiliary means of the other plurality.

19. A variable delivery pump comprising a housing, a main bore substantially central and axially of the housing, a transverse fixed member dividing the main bore into a first and a second compartment, a rotatable drive shaft substantially central of the main bore in the nrst compartment, means axially displaceable along the shaft between a predetermined minimum and maximum limit and inclu-ding a swash plate hav ing at least one face at constant inclination to the shaft and rotatable therewith, a iirst plurality and a second plurality of secondary bores within the housing below the position occupied by the inclined face of the swash plate in the minimum displacement position of the axially displaceable means, each of the secondary bores of the nrst plurality being of a predetermined diameter and each of the secondary bores oi the second plurality being of a diameter smaller than the predetermined diameter, a plunger reciprocably slidable in each secondary bore, a liquid inlet bore in each secondary bore extending to a point external of the housing and adapted to be opened and closed by the reciprocation oi' the respective plunger on rotation of the swash plate, the inlet bore of each secondary bore or the first plurality being so positioned relative the delivery end thereof that it is opened and closed on each reciprocation irrespective of the displaced position of the axially displaceable means while the inlet bore of each secondary bore of the second plurality is so positioned relative the liquid delivery end thereof that it remains closed for each plunger reciprocation when the axially displaceable means occupies a position between the minimum limit and a predetermined position but is opened and closed for each plunger reciprocation when the axially displaceable means is positioned between the predetermined position and the maximum limit, an auxiliary inlet port in each secondary bore of the second plurality positioned adjacent the liquid delivery end thereof, a valve within the auxiliary inlet port biased so that it opens only on the suction stroke ci the plunger within the respective secondary bore while the inlet bore thereof remains closed, spring means pressing one end of each plunger against the swash plate, main spring means tending at all times to press the axially displaceable means to the predetermined minimum limit, secondary spring means resiliently supporting the axially displaceable means on the transverse xed member, liquid 17 channels connecting the delivery end of each secondary bore to the second compartment, a biased valve in each channel closing the channel on each suction stroke of the plunger and tending to open the channel on each delivery stroke thereof, and means for displacing the axially displaceable means including the rotatable swash plate against the main spring means in accordance with the pressure of the delivered liquid in the second compartment including at least one 10 plunger extending from the second compartment 18 into the rst compartment and bearing Within the rst compartment against the axially displaceable means.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,405,006 Ashton July 30, 1946 2,534,153 Widmer Dec. 12, 1950 2,578,561 Lagardelle Dec. 11, 1951 

